Foot prosthesis

ABSTRACT

There is provided a foot prosthesis having especially good gait characteristics. To that end, the prosthesis comprises a first spring element  1  extending from the toe region to the lower leg region and a second spring element  2  extending from the heel region to the lower leg region. The spring elements are formed as leaf-type elements and are connected to each other by their lower leg side first ends  4, 7 . There is provided a tension element  9  which is connected in the forward region of the foot with its one end and connected in the heel region  6  to the second spring element.

The invention relates to a foot prosthesis. From the brochure BIEDERMANNMOTECH, Unterschenkel-Systeme (lower leg systems), page 15, a footprosthesis is known which is formed by a first spring element and asecond spring element connected thereto. The first spring elementextends from the toe region to the lower leg region and is formed in aconvex fashion as viewed from the top. In the lower leg region the freeend supports an adapter for connecting to the lower leg element of aprosthesis. In the region around the ball of the foot the spring elementis firmly connected on its lower side to the upper side of the frontfoot side end of a second spring element by means of screws, whichsecond spring element extends with its free end to the toe region. Thefirst spring element consists of a carbon fiber composite material andhas the appearance of a leaf spring having a width of about 4 cm in theball region and a thickness of 3 to 4 mm.

It is an object of the invention to provide a foot prosthesis with evenbetter gait characteristics.

This object is achieved by a foot prosthesis according to claim 1.

Further embodiments of the invention are characterized in the dependentclaims.

Further features and advantages of the invention will be apparent fromthe description of embodiments with respect to the figures, where

FIG. 1 is a lateral view of a first embodiment of the invention;

FIG. 2 is a corresponding lateral view of a second embodiment;

FIG. 3 is an illustration similar to the one in FIG. 2;

FIG. 4 is a plan view of the object shown in FIG. 3 in the direction ofarrows A′-A; and

FIG. 5 shows the object shown in FIG. 1 in an artificial footrepresented in section.

The first embodiment shown in FIG. 1 comprises a first spring element 1and a second spring element 2. Each of the spring elements is formed ina concave fashion as viewed from the top. The first spring element 1extends with one free end 3 from the toe region to its opposite free end4 which is held in an adapter 5 that can be connected to the lower legportion of a prosthesis. The second spring element 2 extends with one ofits free ends 6 from the heel to its other free end 7 which is held inthe adapter 5.

The bending of the two spring elements is selected such that in theirinoperative position the two ground-side free ends 3, 6 are supportedflat on the ground and the opposite free ends 4, 7 abut in parallelfashion with their convex-side surface, as can be seen in the figure,and are held in a slot 7′ of the adapter 5 and are fixed in the adapter5 by a locking screw 8.

As can be seen from the figures, the front foot region of the firstspring element 1 and the heel region of the second spring element 2 areconnected to each other through a tension element 9. As can be best seenin FIG. 4, the tension element is formed in a ribbon-like manner and isformed as a stretch-free tension ribbon. The tension element 9 isconnected in a tension-proof fashion with one of its ends as close aspossible to the free end 6 of the second spring element 2 using rivets10 and with its other free end close to the free end of the first springelement 1 using rivets 11. The connection location of the rivets 11 isselected such that the first spring element 1 in its normal position isstill located a distance from the ground. This provides the advantagethat during the walking the tension element 9 does not always rest onthe ground and will thus be spared. The connecting location with therivets 11 should be as close as possible to the free end 3 of the firstspring element.

The foot prosthesis formed in this manner provides for especiallyadvantageous gait characteristics starting by setting the foot in itsheel region on the ground and finishing with a rolling movement throughthe front foot.

The embodiment shown in FIG. 2 coincides with respect to the shape ofthe spring elements, the connection to the adapter and the provision ofa tension element.

In order to achieve the advantage that the tension element 9′ is fixedas close as possible to the free ends 3, 6 using the rivets 10, 11 andthat the tension element acts on the outermost free ends on the onehand, and the advantage that the tension element does not completelyrest on the ground on the other hand, there is provided, a distance fromthe free end 3 where the first spring element 1 has just enoughcleareance from the ground, a slit 12 extending along a directiontransverse to the longitudinal direction of the first spring element 1′,as can be best seen in FIG. 4. This slit is desigend to lead the tensionelement 9′ across the slit 12 all the way to the forward free end 3 ofthe first spring element 1′. Starting from the slit 12, the tensionelement 9′ is arranged in closely fitting relationship with the convexportion of the spring element 1′ and is firmly connected thereto in thetoe region by rivets 11, as is best seen in FIG. 2.

Alternatively, it is also possible to arrange the tension element 9 atthe bottom surface of the first spring element 1 and all the way to thefree end, if it is accepted that the tension element will then rest onthe ground.

Referring to FIG. 5, the embodiment described first is introduced intoan artificial foot 13 in a basically known fashion.

1. A foot prosthesis comprising: a first spring element having two freeends, the first free end extends from a toe region and the second freeend extends to a lower leg region; a second spring element extendingfrom a heel region to said lower leg region; said spring elements beingconnected to each other at said lower leg region; and a ribbon-liketension element having two ends, which is connected with its one end toa forward region of the first spring element and connected with itsother end at said heel region of the second spring element, wherein saidtension element is structured and arranged to be able to transmit only atension force between its one end and its other end.
 2. The footprosthesis as claimed in claim 1, further comprising an adapter thatconnects the spring elements at the lower leg region for connection to alower leg portion.
 3. The foot prosthesis as claimed in claim 1, whereinsaid tension element is firmly connected to a ground-side of each ofsaid spring elements.
 4. The foot prosthesis as claimed in claim 1,wherein said first and second spring elements are formed as a concaveshape when viewed from the top.
 5. The foot prosthesis as claimed inclaim 1, wherein said first and second spring elements comprise a carbonfiber composite material and said tension element comprises astretch-free material.
 6. The foot prosthesis as claimed in claim 1,wherein the first and second spring elements are each a leaf springhaving a ground-side surface, the springs being arranged and structuredto rest against each other with their ground-side surfaces facing eachother.
 7. The foot prosthesis as claimed in claim 6, wherein saidtension element is firmly connected to the ground-side surface of theforward region of the first spring element and of the heel region of thesecond spring element.
 8. The foot prosthesis as claimed in claim 6,wherein said tension element is fixed at the forward end of said firstspring element on an upper side thereof such, said first spring elementhaving a slit-like opening in said forward region through which saidtension element is fed toward said second spring element.
 9. The footprosthesis as claimed in claim 1, wherein said tension element is fixedat the forward end of said first spring element on an upper side thereofsuch, said first spring element having a slit-like opening in saidforward region through which said tension element is fed toward saidsecond spring element.
 10. A foot prosthesis comprising: a first springelement having two free ends, the first free end extends from a toeregion and the second free end extends to a lower leg region; a secondspring element extending from a heel region to said lower leg region;said spring elements being connected to each other at said lower legregion; and a ribbon-like tension element having two ends, which isconnected with its one end to a forward region of the first springelement and connected with its other end at said heel region of thesecond spring element, wherein the first and second spring elements areeach a leaf spring having a ground-side surface, the springs beingarranged and structured to contact and rest against each other withtheir ground-side surfaces facing each other.
 11. The foot prosthesis asclaimed in claim 10, wherein said tension element is firmly connected tothe ground-side surface of the forward region of the first springelement and of the heel region of the second spring element.
 12. Thefoot prosthesis as claimed in claim 10, wherein said tension element isfixed at the forward end of said first spring element on an upper sidethereof such, said first spring element having a slit-like opening insaid forward region through which said tension element is fed towardsaid second spring element.
 13. A foot prosthesis comprising: a firstspring element extending from a toe region to a lower leg region; asecond spring element extending from a heel region to said lower legregion; said spring elements being connected to each other at said lowerleg region; and a tension element having two ends, which is connectedwith its one end to a forward region of the first spring element andconnected with its other end at said heel region of the second springelement, wherein said tension element is fixed at the forward end ofsaid first spring element on an upper side thereof such, said firstspring element having a slit-like opening in said forward region throughwhich said tension element is fed toward said second spring element. 14.The foot prosthesis as claimed in claim 13, wherein said first andsecond spring elements are formed as a concave shape when viewed fromthe top.
 15. The foot prosthesis as claimed in claim 13, wherein saidfirst and second spring elements comprise a carbon fiber compositematerial and said tension element comprises a stretch-free material.